자동 로그아웃

function is_user()
{
    $idletime=600; // after 600 seconds the user gets logged out
    if (time()-$_SESSION['timestamp']>$idletime){
        session_destroy();
        session_unset();
    }else{
        $_SESSION['timestamp']=time();
    }

   if (isset($_SESSION['username']))
      return true;
}

로그인 로직에 추가

$_SESSION['timestamp']=time();